Seminars and Events
Coordinador: Rafael Jiménez-Riobóo
10 December 2019, 12:00 h. Salón de Actos
Quantum horizon for silicon nanoelectronics
Dr. Silvano De Franceschi
University Grenoble Alpes & CEA, QUANTECA Lab, IRIG/DEPHY/PHELIQS
Silicon transistors are the building blocks of modern microelectronics. We carry billions of them in our pockets every day. Following decades of uninterrupted development, while transistors have become smaller and smaller,the physics laws governing their operation remain largely classical.
At low temperature, however, new scenarios can emerge. On the one hand, the switching efficiency of silicon transistors can drastically improve enabling the possibility of realizing electronic circuits with reduced power consumption. On the other hand, quantum effects can become prominent opening the possibility to turn transistors into devices capable of encoding elementary bits of quantum information, so-called qubits, through the spin state of localized electronic states.
In Grenoble, the Quantum Silicon Group (https://www.quantumsilicon-grenoble.eu), gathering physicists and engineers from different institutions (CEA,CNRS, and Univ. Grenoble Alpes)), is exploring these opportunities.I will briefly outline our project to develop a scalable quantum processor based on industry-standard silicon technology, and I will discuss research advances, challenges and questions at the engineering and physics level.
1. Gate-based high fidelity spin readout in a CMOS device, Urdampilleta et al., Nat. Nanotechol. 14, 737 (2019)
2. Gate-reflectometry dispersive readout and coherent control of a spin qubit in silicon, Crippa et al.,Nat. Comm. 10, 2776 (2019)
3. Electrical Spin Driving by -Matrix Modulation in Spin-Orbit Qubits, Crippa et al., Phys. Rev. Lett. 120, 137702 (2018)
4. Electrically driven electron spin resonance mediated by spin-valley-orbit coupling in a silicon quantum dot ,Corna et al., npj Quantum Information 4, 6 (2018)
18 November 2019, 12:00 h. Sala de Semarios,182
Molecular Biophysics of Protein Machines
Dr. Fernando Moreno Herrero
National Center of Biotechnology (CNB) CSIC
Many enzymes and proteins involved in the proper functioning and maintenance of the cell appear in a low-copy number. Each molecule counts and proper understanding of a biological process requires monitoring the activity of these individual proteins in action. Multiple biological processes are time resolved and fundamentally mechanical, following a sequence of events coordinated by force, proving again that life is an out of equilibrium process. Traditional biochemical methods lack this single-molecule approach, disregarding individual, out-of-the-mean, behaviors that may be relevant for the proper functioning of the cell.
Manipulation and visualization of single molecules is now possible by means of a myriad of biophysical techniques that capture the presence and activity of single protein machines involved, for instance, in DNA maintenance and repair. These DNA transactions are essential for the cell, attracting much attention of researchers over the last years.
Magnetic Tweezers is based on an inverted optical microscope and provides a measurement of the extension of a single DNA molecule over time at a given force, while proteins are acting on the DNA. I will show our work on Helicases and other proteins involved in DNA repair and chromosome maintenance. Common to all these works is that protein activity is indirectly inferred by changes in the extension of a tethered DNA molecule, thus hindering direct identification of the protein acting on the DNA. Combining MT with fluorescence opens new possibilities to correlate biological activity with the identity of DNA-bound protein complexes and to determine binding positions along DNA.
21 October 2019, 12:00 h. Salón de Actos
Responses of human cells to Sepiolite interaction
Dr. Bernard S. Lopez
Stabilité Instabilité du Génome (SInG), Institut Cochin, Université de Paris
Sepiolite, a fibrous natural hydrated magnesium silicate, is increasingly used in domestic and industrial, cosmetic and pharmaceutical formulations. More specifically, we showed that sepiolite can transfer DNA into mammalian cells, opening alluring avenues for biothechnological and biomedical applications. Importantly, mammalian cells spontaneously internalize sepiolite, facilitating the spontaneous transport and delivery of bound molecules, but increasing the risks of potential toxicity. In addition, the fibrous nature of sepiolite raised health concerns about possible asbestos-like effects, especially because sepiolite can transfer DNA into bacteria through Yoshida effect. In spite that extrapolations from bacteria to mammalian cells could correspond to over-interpretations and the classification by IARC as non-hazardous and non-carcinogenic, we addressed the response of human cells to interactions with sepiolite. We tested three classical cell responses to stress. We show that mammalian cells respond to sepiolite exposure, inducing the production of reactive oxygen species and the expression of inflammatory cytokines. This shows that cells detect sepiolite contamination and respond. Remarkably, sepiolite exposure did not alter the cell cycle distribution and triggers neither the DNA damage response program nor apoptosis, suggesting that it does not significantly assault the genetic material in mammalian cells. The potential toxicity of chronic versus transient exposure to sepiolite will be discussed.